Setting HTML meta elements with knitr

Question

I'm generating HTML reports using knitr, and I'd like to include author and generation date meta tags.

My Rhtml page looks something like this.

<html>
<head>
  <meta name="author" content="<!--rinline Sys.getenv('USERNAME') -->">
  <meta name="date" content="<!--rinline as.character(Sys.time()) -->"> 
</head>
<body>
</body>
</html>

Unfortunately, after I knit("test.Rhtml"), the HTML that knitr generates is

  <meta name="author" content="<code class="knitr inline">RCotton</code>">
  <meta name="date" content="<code class="knitr inline">2013-01-02 14:38:16</code>">

which isn't valid HTML. What I'd really like to generate is something like

  <meta name="author" content="RCotton">
  <meta name="date" content="2013-01-02 14:38:16">

Can I generate R code that doesn't get a code tag wrapping it? Or is there another way to specify tag attributes (like these content attributes)?

So far my least-worst plan is to manually fix the content with readLines/str_replace/writeLines, but this seems rather kludgy.

You might also simply `brew` that file. – daroczig Jan 02 '13 at 15:04 — daroczig, Jan 02 '13 at 15:04

score 13 · Accepted Answer · answered Jan 02 '13 at 17:37

13

Another (undocumented) approach is to add I() around your inline code to print the characters as is without the <code> tag, e.g.

<html>
<head>
  <meta name="author" content="<!--rinline I(Sys.getenv('USERNAME')) -->">
  <meta name="date" content="<!--rinline I(as.character(Sys.time())) -->"> 
</head>
<body>
</body>
</html>

answered Jan 02 '13 at 17:37

Yihui Xie

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I believe the newly added `knit_expand` function would be ideal here. By passing a file through `knit_expand` first and then `knit2html`, you can easily achieve the best of `brew` and `knitr`. Maybe @Yihui can add to this. – Ramnath Jan 03 '13 at 18:19
@DieterMenne sure, I'll add to the website; @Ramnath in this case, `` is not a bad choice if there are further chunks in the file, and `knit_expand()` will be an additional step before `knit()` – Yihui Xie Jan 03 '13 at 21:17
@yihui Makes sense. But knit_expand provides `brew` like functionality which has been long sought for by Sweave users. One way to reduce the tool chain is to allow users to specify `opts_knit$set(expand = TRUE)` which will run the document through `knit_expand` before knitting it. Alternately, it can be achieved using the document hook, which I think makes more sense since knit_expand can then use data from the parent frame. – Ramnath Jan 04 '13 at 18:07

score 4 · Answer 2 · answered Jan 02 '13 at 16:30

Not really nice, but seems to work without adding a hook:

<head>
<!--begin.rcode results='asis', echo=FALSE
cat('
  <meta name="author" content="', Sys.getenv('USERNAME'), '"> 
  <meta name="date" content="', as.character(Sys.time()),'-->"> 
',sep="")
end.rcode-->

</head>

Setting HTML meta elements with knitr

2 Answers2

Linked